1. Field of the Invention
The present invention relates to a muffler, and more particularly to a muffler affixed to an exhaust apparatus of a motor vehicle for noise attenuation.
2. Description of Related Art
Generally, an exhaust apparatus is equipped to prevent an exploding sound generated when combustion gas of high temperature and high pressure generated from an engine explosion is emitted into the air and to prevent emission of harmful gases.
The aforementioned exhaust apparatus includes, as illustrated in FIG. 4, an exhaust pipe 51, servo and main muffler 52 and 53, and a catalytic converter 54.
In other words, pressure and vibration are attenuated when the combustion gas emitted through an exhaust port of an engine is exhausted outside via the catalytic converter 54 and the servo and main mufflers 52 and 53.
The main muffler 53 thus described includes, as illustrated in FIG. 5, a housing 55, first, second and third baffles 60, 61 and 62, a first pipe 63, a second pipe 64 and a third pipe 65, where the second baffle 61 is formed with an air hole 66.
When the combustion gas of high pressure and high temperature is input into the housing 55 via the exhaust pipe 51 and sequentially into first, second, third and fourth chamber 56, 57, 58 and 59, the gas is abruptly expanded to reduce its temperature and pressure.
Specifically, when the combustion gas is infused into the respective chambers 56, 57, 58 and 59, pulsation generated from the engine is reduced by resonance, whereby the pressure and the temperature are dropped to attenuate the exhaust noise during exhaustion thereof.
The pulsation reduction by way of resonance is appropriately established by volumes of respective chambers 56, 57, 58 and 59, and lengths and diameters of the exhaust pipe 51 and pipes.
However, there is a problem in that the aforementioned noise attenuation effect is sharply reduced when exhaustion pressure is outside of a predetermined exhaust pressure range because the exhaustion pressure changes according to revolution per minute (RPM) of the engine.
In other words, the above described conventional muffler is designed according to an average exhaust pressure at high and low speeds, so that, when a running speed of a vehicle is outside of escapes the average exhaust pressure, the silencer attenuation effect is decreased, thereby increasing the noise of the running vehicle.